build: Remove build system support for gold plugin, except under ChromeOS.

build/toolchain/toolchain.gni

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Toolchain-related configuration that may be needed outside the context of the
 # toolchain() rules themselves.
 
 import("//build_overrides/build.gni")
 import("//build/config/chrome_build.gni")
 
@@ skipping 42 matching lines @@
 # The path to the hermetic install of Xcode. Only relevant when
 # use_system_xcode = false.
 hermetic_xcode_path =
     rebase_path("//build/${target_os}_files/Xcode.app", "", root_build_dir)
 
 declare_args() {
   if (is_clang) {
     # Clang compiler version. Clang files are placed at version-dependent paths.
     clang_version = "5.0.0"
   }
-
-  # Set to true to use lld, the LLVM linker. This flag may be used on Windows
-  # or Linux.
-  use_lld = (is_win && host_os != "win") ||
-            (allow_posix_link_time_opt && target_os == "linux" &&
-             !is_chromeos && target_cpu == "x64")
 }
 
 # Check target_os here instead of is_ios as this file is loaded for secondary
 # toolchain (host toolchain in particular) but the argument is the same for
 # all toolchains.
 assert(!use_xcode_clang || target_os == "ios",
        "Using Xcode's clang is only supported in iOS builds")
 
 # Subdirectory within root_out_dir for shared library files.
 # TODO(agrieve): GYP sets this to "lib" for Linux & Android, but this won't work
@@ skipping 41 matching lines @@
   _tool_wrapper_path =
       rebase_path("//build/toolchain/win/tool_wrapper.py", root_build_dir)
 
   stamp_command = "$python_path $_tool_wrapper_path stamp {{output}}"
   copy_command =
       "$python_path $_tool_wrapper_path recursive-mirror {{source}} {{output}}"
 } else {
   stamp_command = "touch {{output}}"
   copy_command = "ln -f {{source}} {{output}} 2>/dev/null || (rm -rf {{output}} && cp -af {{source}} {{output}})"
 }